linux-kernel - Re: __get_free_pages: can GFP_DMA omit GFP_KERNEL and GFP

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Date:	Mon, 4 Jun 2007 15:07:27 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Christoph Lameter <clameter@....com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: __get_free_pages:  can GFP_DMA omit GFP_KERNEL and GFP_ATOMIC?

On Mon, 4 Jun 2007, Christoph Lameter wrote:

> On Mon, 4 Jun 2007, Robert P. J. Day wrote:
>
> > all right, then some of those __get_free_pages() calls would translate
> > to calls of the form __get_dma_pages(0, ...) -- is that what you're
> > saying?  or would it be equivalent and preferable to put GFP_ATOMIC in
> > there just so it looks not so weird?
>
> Put GFP_ATOMIC in there so that it does not look weird.
>
> GFP_ATOMIC & ~__GFP_HIGH == GFP_NOWAIT
>
> So these should have GFP_NOWAIT as far as I can tell?

beats me.  just FYI, it's not like this would be a massive change --
here's the entire collection of candidates for conversion over to
__get_dma_pages():

$ grep -r "get_free.*GFP_DMA" *
arch/s390/kernel/smp.c:                 __get_free_pages(GFP_KERNEL | GFP_DMA,
drivers/net/arm/ep93xx_eth.c:           page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
drivers/net/arm/ep93xx_eth.c:           page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
drivers/s390/net/qeth_main.c:                   ptr = (void *) __get_free_page(GFP_KERNEL|GFP_DMA);
drivers/s390/net/claw.c:                        (void *)__get_free_pages(__GFP_DMA,
drivers/s390/net/claw.c:                        (void *)__get_free_pages(__GFP_DMA,
drivers/s390/net/claw.c:                   p_buff=(void *)__get_free_pages(__GFP_DMA,
drivers/s390/net/claw.c:                        (void *)__get_free_pages(__GFP_DMA,
drivers/s390/net/claw.c:                        p_buff = (void *)__get_free_pages(__GFP_DMA,
drivers/s390/block/dasd.c:      device->ccw_mem = (void *) __get_free_pages(GFP_ATOMIC | GFP_DMA, 1);
drivers/s390/char/tty3270.c:                    __get_free_pages(GFP_KERNEL|GFP_DMA, 0);
drivers/s390/char/sclp_cpi.c:   sccb = (struct cpi_sccb *) __get_free_page(GFP_KERNEL | GFP_DMA);
drivers/s390/cio/cmf.c:         mem = (void*)__get_free_pages(GFP_KERNEL | GFP_DMA,
lib/swiotlb.c:          io_tlb_start = (char *)__get_free_pages(GFP_DMA | __GFP_NOWARN,
lib/swiotlb.c:  io_tlb_overflow_buffer = (void *)__get_free_pages(GFP_DMA,
sound/oss/sscape.c:             start_addr = (char *) __get_free_pages(GFP_ATOMIC|GFP_DMA, sz);
sound/oss/hal2.c:       codec->buffer = (unsigned char *)__get_free_pages(GFP_KERNEL | GFP_DMA,
sound/oss/dmabuf.c:             start_addr = (char *) __get_free_pages(GFP_ATOMIC|GFP_DMA|__GFP_NOWARN, sz);

  and, obviously, it's not worth doing anything under sound/.  so
we're not talking enormous cleanup or anything.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
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